AC line triggered refreshing of CRT displays

Claim 2

A display system for displaying symbols on a display device that exhibits a scan-line raster, said display system including a circuit for controlling the generation of signals for the display of symbols in defined character block on said device comprising means for generating a plurality of pulses, means for counting said pulses, decoder means responsive to the count in said counting means to define the scan line raster and to divide said blocks into rows and columns of elemental spaces selectively illuminated to dislay symbols in said blocks, said decoder means disabling said counter from counting further upon a predetermined count being in said counter indicating a complete raster scan on said display device, means for periodically reenabling said counter to count in response to said pulses, the reenabling of said counter resulting in another complete raster scan on said display device.

Claim 3

The display system in accordance with claim 1 wherein said counting means comprises a first plurality and a second plurality of counter stages and said decoder disables said second plurality of counter states from counting upon said predetermined count being therein.

Claim 4

The display system in accordance with claim 2 wherein said counter reenabling means comprises a latching circuit which is placed in a first state by said decoder, said latching means is periodically placed in a second state, and said second plurality of counter means is responsive to said latching means being in said first state to be disabled from counting and is responsive to said latching means being said second state to be enabled to count.

Claim 5

A display system for displaying characters on a display device that exhibits a scan-line raster and wherein each character is displayed in one character block on said display device, said display system including a character generator generating signals for the display of characters on said display device, and a circuit for controlling the operation of said character generator comprising a first counter driven by a pulse train, a second counter driven by said first counter, decoder means responsive to the count in said first and said second counters for controlling the operation of said character generator, said decoder means generating a first signal upon a predetermined count being in said first and said second counter indicating a complete raster scan on said display device, and latching means being placed in a first state responsive to said first signal generated by said decoder means, said second counter being disabled from counting responsive to said latching means being in said first state, and said disabled second counter preventing a subsequent complete raster scan on said display device.

Claim 6

A display system for displaying characters on a display device that exhibits a scan-line raster and wherein each character is displayed in one character block on said display device, said display system including a character generator generating signals for the display of characters on said display device, and a circuit for controlling the operation of said character generator comprising a first counter driven by a pulse train, a second counter driven by said first counter, decoder means responsive to the count in said first and said second counters for controlling the operation of said character generator, said decoder means generating a first signal upon a predetermined count being in said first and said second counter indicating a complete raster scan on said display device, and latching means being placed in a first state responsive to said first signal generated by said decoder means, said second counter being disabled from counting responsive to said latching means being in said first state, and said disabled second counter preventing a subsequent complete raster scan on said display device.

Claim 7

The display system in accordance with claim 4 further comprising means for generating a second signal in response to each cycle of an alternating current power source providing power to said display system, said latching means being responsive to said second signal to be placed in a second state thereby reenabling said second counter to count.

Claim 8

The display system in accordance with claim 5 wherein said decoder is responsive to a first predetermined count in said first and said second counters following reenabling of said second counter to generate a third signal, said second counter being reset to a second predetermined count in response to said forth signal.

Claim 9

A display system for displaying characters comprising a display device that exhibits a scan-line raster and wherein each character is displayed in a character block on said device, a character generator generating signals for the display of characters on said display device, and a circuit for controlling the operation of said display system comprising an oscillator a first binary counter being driven by said oscillator a second binary counter being driven by said first counter, said second counter counting from a first predetermined count, decoder means responsive to the count in said first and second counters to define the scan line raster and to divide said character blocks into rows and columns of elemental spaces selectively illuminated to display characters therein, said decoder controlling said character generator and generating a first signal upon a second predetermined count being in said first and second counters, a latching circuit having a first and a second state, said latching circuit being placed in said first state responsive to said first signal, said second counter being disabled from counting responsive to said latching circuit being in said first state, said disabled second counter preventing a subsequent complete raster scan on said display device, said means for generating a second signal in response to each cycle of an alternating current power source providing power to said display system said second signal causing said latching means to switch to said second state and thereby reenable said second counter to count, and said decoder being responsive to a third predetermined count in said second counter to generate a third signal causing said second counter to be reset to said first predetermined count.

Claim 10

A display system for displaying characters comprising a display device that exhibits a scan-line raster and wherein each character is displayed in a character block on said device, a character generator generating signals for the display of characters on said display device, and a circuit for controlling the operation of said display system comprising an oscillator a first binary counter being driven by said oscillator a second binary counter being driven by said first counter, said second counter counting from a first predetermined count, decoder means responsive to the count in said first and second counters to define the scan line raster and to divide said character blocks into rows and columns of elemental spaces selectively illuminated to display characters therein, said decoder controlling said character generator and generating a first signal upon a second predetermined count being in said first and second counters, a latching circuit having a first and a second state, said latching circuit being placed in said first state responsive to said first signal, said second counter being disabled from counting responsive to said latching circuit being in said first state, said disabled second counter preventing a subsequent complete raster scan on said display device, said means for generating a second signal in response to each cycle of an alternating current power source providing power to said display system said second signal causing said latching means to switch to said second state and thereby reenable said second counter to count, and said decoder being responsive to a third predetermined count in said second counter to generate a third signal causing said second counter to be reset to said first predetermined count.

Claim 11

The display system in accordance with claim 7 further comprising means controlled by said decoder means for generating horizontal and vertical synchronization signals, and means for mixing said character signals generated by said character generator and said horizontal and said vertical synchronization signals into a video signal.

Claim 12

The display system in accordance with claim 8 wherein said display device comprises a one-shot ramp horizontal deflection signal generator generating one horizontal deflection signal in response to each horizontal synchronization signal in said video signal, and a one-shot ramp vertical deflection signal generator generating one vertical deflection signal in response to each vertical synchronization signal in said video signal.